The present invention relates to a method for transferring a stimulable phosphor sheet which is favorably employed in a double-side image reading procedure of a radiation image recording and reproducing system.
As a method replacing a conventional radiography, a radiation image recording and reproducing method utilizing a stimulable phosphor was proposed and has been practically employed. The method employs a stimulable phosphor sheet (i.e., radiation image storage panel) comprising a stimulable phosphor, and comprises the steps of causing the stimulable phosphor of the phosphor sheet to absorb radiation energy having passed through an object or having radiated from an object; sequentially exciting the stimulable phosphor with an electromagnetic wave such as visible light or infrared rays (hereinafter referred to as xe2x80x9cstimulating raysxe2x80x9d) to release the radiation energy stored in the phosphor as light emission (i.e., stimulated emission); photoelectrically detecting the emitted light to obtain electric signals; and reproducing the radiation image of the object as a visible image from the electric signals. The phosphor sheet thus treated is then subjected to a step for erasing a radiation image remaining therein, and then stored for the next recording and reproducing procedure. Thus, the stimulable phosphor sheet can be repeatedly employed.
The stimulable phosphor sheet has a basic structure comprising a support and a stimulable phosphor layer provided thereon. If the phosphor layer is self-supporting, the support may be omitted. On the free surface (surface not facing the support) of the phosphor layer, a transparent protective film is generally placed to keep the phosphor layer from chemical deterioration or physical damage.
The radiation image recorded in the stimulable phosphor sheet is generally read by the steps of applying stimulating rays onto the top surface side (phosphor layer side) of the phosphor sheet, collecting light (i.e., stimulated emission) emitted by the phosphor particles by means of a light-collecting means from the same side, and photoelectrically converting the light into digital signals of image. A system for reading the image from one side of the phosphor sheet in this manner is referred to as xe2x80x9csingle-side reading systemxe2x80x9d. However, there is a case that the light emitted by the phosphor particles should be collected from both sides (i.e., front and back surface sides) of the phosphor sheet. For instance, there is a case that the emitted light should be collected as much as possible. There is also a case that the radiation image recorded in the phosphor layer varies along the depth of the phosphor layer, and that the variation should be detected. A system for reading the image from both sides of the stimulable phosphor sheet is referred to as xe2x80x9cdouble-side reading systemxe2x80x9d.
A radiation image storage panel employed in the double-side reading system, as well as a panel employed in the single-side reading system, is desired to be as sensitive as possible and to provide a radiation image of high quality (high sharpness, high graininess, etc.). The double-side reading system is described in Japanese Patent Provisional Publication No. 55-87970.
In the apparatus for the double-side reading system illustrated in the Japanese publication, the stimulable phosphor sheet is conveyed by means of a pair of nip rollers which drive the phosphor sheet to horizontally move by driving force directly applied to both surfaces of the phosphor sheet. The simulating rays such as a laser beam are applied onto the top surface of the phosphor sheet, and the stimulated emission radiated from the inside of the phosphor sheet is detected from both of the top and back surface sides. The stimulable phosphor sheet thus treated is further conveyed by means of the nip rollers which apply driving force onto both surfaces of the phosphor sheet, and successively exposed to erasing light radiated from the erasing light sources for performing the erasing procedure.
As is described above, both surfaces of the stimulable phosphor sheet are moved in contact with a pair of rollers which in combination give driving force to the phosphor sheet. Therefore, the phosphor sheet is apt to get scratches and/or stains on its surfaces after employment in the repeated radiation image recording and reproducing procedures. The presence of scratches and stains on the surfaces of the stimulable phosphor sheet gives adverse effects such as lowering of an image quality to a radiation image reproduced from the phosphor sheet.
It is an object of the present invention to provide a method for transferring a stimulable phosphor sheet in a radiation image recording and reproducing method.
It is another object of the invention to provide a method for transferring a stimulable phosphor sheet which is favorably employable during the double-side radiation image reading procedure.
The present invention resides in a method for transferring a stimulable phosphor sheet which comprises holding and driving the stimulable phosphor sheet by a set of rollers which are placed on both edge sides of the phosphor sheet, at least one of the rollers being rotated by a driving force provided by a driving means.
The invention also resides in a method for transferring a stimulable phosphor sheet containing a radiation image therein during a radiation image reading step comprising sequentially applying stimulating rays onto the phosphor sheet to excite the stimulable phosphor sheet whereby releasing radiation energy from the radiation image as light emission and collecting the light emission from both surface sides of the phosphor sheet, which comprises holding and driving the stimulable phosphor sheet by a set of rollers which are placed on both edge sides of the phosphor sheet, at least one of the rollers being rotated by a driving force provided by a driving means.